2-amino-6-mercaptopurine



United States Patent 1 Claim. (Cl. 260252) The present invention relates to purine compounds and more particularly to 6-mercaptopurine compounds of exceptional activity as inhibitors of micro-organisms. The compounds are active in this respect, in the inhibition of lactic acid bacteria and for their bacterio-static eifect. Compounds of this nature are also valuable for their antileukemic activity and in treating other forms of neoplastic growth, as described in Patent No. 2,697,709, of which the present application is a continuation. Advanced studies have disclosed that these derivatives are of exceptional interest, and have related properties'and value for the indicated applications. The compounds, particularly thioguanine, are useful in producing remissions in acute leukemia. The-compounds, however, do not cure the condition. i

The compounds of the present invention are members of the class represented by the general formula:

.....r l Z where R and R are selected from the class consisting of H,lower alkyl and aryl radicals; RRN is selected from the class consisting of cyclic amino radicals; and R and R together have no more than six carbon atoms.

Compounds of this nature may be conveniently prepared by the reaction of a compound having the formula:

wherein RRN has the indicated values with phosphorus pentasulfide in a basic solvent which is inert to the phosphorus pentasulfide. This reaction can be carried out in an inert solvent such as tetralin, but the yields are less satisfactory. ,fSuitablebases for the purpose are those relatively inert toward the reagents entering into the reactions and preferably those boiling over 100, allowing the reaction to proceed 'without the use of pressure equipment. Effectively, for example, amino-substituted aromatic compounds would be unsuitable because of their reactiveness under the conditions involved. Bases capable of operating efiectively under the conditions involved include pyridines, picolines, lutidines, quinoline and perhaps isoquinoline. Although the suitability of any number of bases for the purpose is easily ascertained, the availability of pyridine makes this compound preferable in the ordinary practice of the invention. In general the heterocyclic bases may be preferred because they are sufficiently involatile, sufiiciently basic and nonreactive toward the components of the reaction.

The advantages of the present invention are improved yield, much greater .ease of purification and greater convenience in manufacture due to the lower operating temare illustrative.

2 EXAMPLE 1 2-amin0-6-mercapt0purine A mixture of 20 g. of guanine, 100 g. of phosphorus pentasulfide and 500 ml. of pyridine was refluxed for six hours. The pyridinewas removed under reduced pressure and the residue boiled with 500 ml. of water for 10 minutes. The pH was adjusted to 4 by the addition of concentrated hydrochloric acid and the mixture was chilled. The precipitate was filtered ofl, washed with water and dried at 100. This precipitate was extracted four times with 200 ml. portions of concentrated ammonium hydroxide and the insoluble residue filtered off. The ammoniacal solution was evaporated to 500 ml. to remove some of the excess ammonia and the solution then acidified to pH '4 by the addition of concentrated hydrochloric acid. The precipitate of 2-amino-6-mercaptopurine (11.7 g.) was purified by solution in dilute ammonium hydroxide and precipitation at pH 4. The product has a characteristic ultraviolet absorption spectrum with maxima at 255 and 345 my. at pH 1, and at 245, 270 and 322 mp. at pH 11.

EXAMPLE 2 A mixture of 1 g. of guanine, 3 g. of phosphorus pentasulfide and 50 ml. of quinoline was warmed to about 120 for 45 minutesfand then at 175 for 30 minutes.

After cooling slowly the solvent was decanted and the residue extracted with hot water and filtered. The solid was warmed with 8 N ammonium hydroxide and filtered. The filtrate was boiled until neutral during which time a dark granular precipitate'was formed. This was removed by filtration and washed with methanol. The yield was 450 mg. of material possessing the ultraviolet absorption spectrum of 2-amino-6-mercaptopurine, as given above.

EXAMPLE 3 Z-diniethylamino-ti-hydroxypurine 2-dimethylam ino-6-mcrcaptopurine mixture of 5.5 g. of 2-dimethylamino-6-hydroxypurme, 25 g. of phosphorus pentasulfide and 250 m1. of

dry pyridine was heated under reflux conditions for 3 hours. The reaction mixture was evaporated to dryness under reduced pressure and the residue heated with peratu'reswhich can be used. The following" examples 9 v washeated at"140ina"sealed"tube fol-24 hours." The 200 ml. of water for 20 minutes. After chilling, the solid residue was collected, washed with cold water and dried at The crude 2-dimethylamino-6-mercaptopurine (3.75 g.) was purified by recrystallization from water followedv by solution in 2-N hydrochloric acid reprecipitation by neutralization with ammonium hydroxide. The purified product showed an ultraviolet absorption spectrum with A max.=270 and 358 mu at pH 1 and ..max.=255, 283, 330 m at pH 11.

v EXAMPLES 2-ethylamino-6-hydroxypurine A mixture of 30 g. of 2 'methyImerca topurine-G-hydroxypurm'e and 6100 ml; of 33% aqueousfethylamihe EXAMPLE 6 1 hy 4m1' no- -merantom4ri A mixture of 5.6 g. 2:ethyl-amino-6hydroxypurine, 30 g. of phosphorus pentasulfide and 250 ml. of pyridine was heated under reflux conditions for 4. hours. he mixture was taken to dryness under reduced pressure, and the residue was heated with 100 ml. of water for 15 minutes. The solution was chilled and 150 ml. of concentrated ammonium hydroxide added. After further chilling the precipitate of ammonium phosphate was filtered off and the ammoniacal filtrate taken down to 25 ml. under reduced pressure. Upon chilling, 2- ethylamino-6-mercaptopurine (2.5 g.) separated out and was collected. The product has an ultraviolet absorption spectrum with A max.=262 and 350 m at pH 1 and A max.=250, 325 m at pH 11.

EXAMPLE 7 2-anilino-6-hydroxypurine A mixture of 30 g. of 2.-methy lme rcapto-6 hydroxy- Purine d m o ni ine a ea d t 160 m 3 hours. The reaction mixture was diluted with 299 f b lu alcohol nd h nsoluble re d e fil ered 911?. This residue was then leached with 290 ml. of e h and dried at 1 11 em er ture The g ade annino-ehydr xypur wa ola d a its h hle ide a) y l n i h .2 0 m f H! h d a: chloric acid, filtering chilling. The hydrochloride was suspended in 500 ml. of hot water and the theoretical amount of sodium hydroxide added to neutralize the hydrochloric acid. The free 2-anilino-6-hydroxypurine (19.5 g.) was collected after chilling. It has an ultraviolet absorption spectrum with A max,==270 ms a 19 v 1 a d A ma -=2 Q 2 .111 at PH 1 EXAMPLE 8 wa i er awe w ce A mixture of 19 g. of '2-anilino-6-hydroxypurine, 50 g. of ground phosphorus pentasulfide and 200 ml. of dry pyridine was heated under reflux conditions for 5 hours. The reaction mixture was worked up essentially as in Example 4. For final purification, the product was dissolved in parts of dimethyl formamide, the insoluble residue removed by filtration and the 2-anilino- G-mercaptopurine precipitated by the addition of 10 volumes of water for every volume of dimethyl formamide. The product has an ultraviolet absorption spectrum with A max.=28(), 352 me at pH 1 and A max.= 285, 327 m at pH 11.

EXAMPLE 9 2-piperidina-6rhydroxypurine A mixture of 30 g. of 2-methylmercapto-6hydroxypurine, 65 ml. of piperidine and 27.5 ml. of concentrated hydrochloric acid was heated at 140 in a sealed vessel for 24 hours. The reaction mixture was diluted with 50 ml. of water and filtered to remove a small residue. The solution was adjusted to pH 5 with hydrochloric acid and chilled. The precipitate, which contained mainly starting material, was filtered off. The filtrate was taken to' dryness under reduced pressure and the residue treated with 100 ml. of 6-N hydrochloric acid and 15.0 ml. .of acetone. The 2+piperidinoyd..mxyp in P ec pi a e a its dtqshl'qt de ,(5- 55).- t o ained a t e t e ss?- y re ation 4 water and neutralization with ammonium hydroxide. The product has an ultraviolet absorption spectrum with A max.=260 m at pH 1 and A max.=255, 290 (infl.) at pH 11.

EXAMPLE 10 2-piperidino-6-mercapzfopurine mixture of 7 g. of 2-piperidino 6-hydroxypurine, 50 g. of powdered phosphorus pentasulfide and 500151. dry pyridine was heated under reflux conditions for 3 hours. The reaction mixture was Worked 11p as described in Example 4. The 2-piperidino-6-mercaptopurine (4.1 g.) was purified by solution in dilute ammonium hydroxide and precipitation at pH 5 with acetic acid. The product has an ultraviolet absorption spectr n with x" n a .=2'72, 358 mp at pH 1 and A max. 55 20 mwP EXAMPLE 11 Z-ziimezhylwm'ino-ti-mercwptopurine A mixture of 15 g. of 2-methylmercapto-6-hydroxy; purine and '30 ml. r 30% methanoli-c dimethylamine was heated at 140 for 24 hours in a sealed tube. mixture taken to dryness under reduced'pressure The due was dissolved in ml. of'b oiling i-N h- QIQQhJQrrc acid filtered hot to removean insoluble due, The filtrate adjusted to pH 6 with amnionr hydroxide. After chilling, the 2- dimethylalm' o-6-hy} droxypurine (8.5 g.) was filtered ofli washedwith' water and err d at 110.

A mixture of 5 g. of Z-dimethylamino-6-hydroxypurine, 25 g. of phosphorus pentasulfide and 250 ml. of dry pyridine was refluxed for three hours. The excess pyridine was removed by distillation under reduced pressure. The residue was boiled with 200 ml. of water for hour then chilled. The precipitate of crude Z-dimethylamino-6-mercaptopurine was filtered 01f and washed water. It purified by solution in 200 mil of dilute ammonium hydroxide, filtration and acidification to 5 with hydrochloric acid. The yield of purified product Five grams of 2-methylimercapto-6-hydroxypurine and 20 ml. of 14% methanolic methylamine were heated in a sealed vessel at for 19 hours. The reaction mixture was taken to dryness in vacuo and the residue dissolved in 10 ml. of concentrated hydrochloric acid ns159 m f-w e e ol as l ere a d 1 traliz ed with ammonium hydroxide, whereupon 2-metliylamino-6-hydroxypurine (2.7 g.) precipitated.

A mixture of 2.7 g. of 2-methylamino-6-hydroxypurine, 4 g. of pulverized liver of sulfur and 15 g. of phorus pentasulfide and 100 cc. of tetralin was'heated at 2Q 0ffor 10 hours with mechanica-l stirring. "After pooling, the insoluble material was filter'ed'pfi, washed with benzene and dried. It was then treated with 250 of water and 15 ml. of concentrated hvdrQXide an amd to boiling T e ammo ia 'a s lution was filtered and acidified with glacial acetic After cooling, the precipitate of Z-me thyI-amino-Q-mencaptopurine was collected, washed with water and dried at 10 0. Its ultraviolet absorption spectrum closely resembles that of 2-amino -6-mercaptopurine.

This application is a continuation-impart of our copending applications Serial No. 364,947ffiled June 29, '1953 and Serial No. 375,819, filed August 21, 1953bdth a a an o e What we claim is:

2-amino-6-mercaptopurine.

References Cited in the file of this patent 

